Technical Field
The instant disclosure relates to a charging system, and particularly relates to a wireless charging system.
Related Art
Wireless charging technology is also called non-contact charging technology. In the technology, wires can be omitted, so that a user can be prevented from getting electric shock; furthermore, since wireless charging does not need wall sockets, problems of winded wires can be prevented. The wireless charging technology improves the safety and convenience in power charging and transmission, accordingly, products applied with wireless charging technologies are widely available on the market.
The wireless charging technologies utilize the electromagnetic induction principle for power transmission. In detail, a charger transmits power to an electronic device by coil coupling, wherein the charger comprises a wireless power transmitter, and the electronic device comprises a wireless power receiver. A primary coil of the wireless power transmitter is closely attached to a mating secondary coil of the wireless power receiver for power transmission. After the primary coil is electrified, the primary coil generates a magnetic field. Next, the secondary coil is affected by the magnetic field to generate an inductive current. And then, a rectifying circuit of the wireless power receiver converts the inductive current into a direct current. Hence, the electronic device receives the direct current for charging. Accordingly, the power is transmitted from the charger to the electronic device.
In addition, the wireless power receiver can generate power control signals (or called packets) according to the received power and transmit the power control signals to the wireless power transmitter for power control and program control. And then, the wireless power transmitter adjusts the power to be transmitted according to the power control signal. Accordingly, in the conventional, the wireless power receiver modulates the power control signals and then transmits the modulated power control signals. The wireless power transmitter demodulates the modulated power control signals to obtain the power control signals. However, the filter of the demodulation circuit in the conventional wireless power transmitter is complicated, so that the circuit cost is increased and the circuit design is rather difficult.